Restarting device of a pump

ABSTRACT

An object of the present invention is to provide a restarting device of a pump for restarting an operation of the pump automatically in such an event that the operation of the pump is shut down due to a change-over valve stopping in an intermediate position, which valve has been moved forth and back to switch a direction for a center rod of the pump to move.  
     A restarting device of a pump according to the present invention comprises a center rod defining fluid delivering chambers and driving chambers  11   b  and  12   b,  in which when said center rod is driven toward one side, a driving fluid is supplied into one driving chamber  11   b  located in one side thereof so as to discharge a fluid-in-transfer in one fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the other fluid delivering chamber located in the other side of the center rod while the driving fluid in the other driving chamber  12   b  located in said other side being discharged, and when the center rod is driven toward the other side, the driving fluid is supplied into said other driving chamber  12   b  located in the other side of the center rod so as to discharge the fluid-in-transfer in said other fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into said one fluid delivering chamber located in said one side of the center rod while the driving fluid in said one driving chamber  11   b  located in said one side being discharged, so that the fluid-in-transfer may be continuously transferred by the reciprocating motion of said center rod, said restarting device of the pump further comprises: a change-over valve  2  for switching a direction for said center rod to move; and a restarting hydraulic circuit  3  which when a supply of the driving fluid from said change-over valve  2  to the driving chambers  11   b  and  12   b  in both sides is stopped, detects the supply of the driving fluid into the driving chambers  11   b  and  12   b  in both sides having been sopped and then causes the driving fluid to flow into said change-over valve, thereby restarting the supply of the driving fluid into said driving chambers  11   b  and  12   b.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a restarting device of a pump for restarting an operation of the pump automatically in such an event that the operation of the pump is shut down due to a change-over valve stopping in an intermediate position, which valve is to be moved forth and back to switch a direction for a center rod of the pump to move.

[0002] Some pumps, for example, diaphragm-type pumps according to the prior art have employed such a configuration, in which the pump comprises a center rod provided with diaphragms in both sides thereof for defining fluid delivering chambers and driving chambers respectively, and when the center rod is to be driven toward one side, a driving fluid (e.g., a compressed air) is supplied into the driving chamber located in said one side of the center rod so as to discharge a fluid-in-transfer in the fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the fluid delivering chamber located in the other side of the center rod while the driving fluid in the driving chamber located in said other side being discharged, and when the center rod is to be driven toward the other side, the driving fluid is supplied into the driving chamber located in said other side of the center rod so as to discharge the fluid-in-transfer in the fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into the fluid delivering chamber located in said one side of the center rod while the driving fluid in the driving chamber located in said one side being discharged, so that the fluid-in-transfer may be transferred continuously by this reciprocating motion of the center rod.

[0003] Said diaphragm-type pump is provided with a change-over valve which moves forth and back in order to switch a direction for the center rod to move. That change-over valve has a spool. The spool is provided with a pair of pressure chambers each being disposed in each side of the spool along the direction of movement for switching the direction for the spool to move. In the change-over valve, a differential pressure is generated between each of the pair of pressure chambers at the terminal end of the moving stroke of the center rod so as to switch a position of the spool.

[0004] However, if the liquid prepared as the fluid-in-transfer includes air in it, the operation of the diaphragm may possibly become unstable to stop the spool of the change-over valve in an intermediate position along the direction of its reciprocating motion.

[0005] Further, in a case of insufficient supply of the driving fluid, the differential pressure between each of the pair of pressure chambers will decrease and there will be a shortage of energy to move the spool, resulting in the spool stopping in the intermediate position.

[0006] Further, in a case where a compressed air is used as the driving fluid, when the compressed air to be supplied to the change-over valve is delivered into the change-over valve, the pressure of the compressed air might possibly drop rapidly and cause a low temperature in the change-over valve by adiabatic expansion to lead to a partially frozen condition thereof, resulting in the spool stopping in the intermediate position.

[0007] If the spool stops in the intermediate position, supply of the driving fluid to the driving chamber is stopped and thus the operation of the pump is shut down. To solve that problem, an inventive attempt has been taken, in which a snap spring is attached to one end portion of the spool so that a bias force of the snap spring may be used to prevent to the utmost the spool from stopping in the intermediate position, but there is still a possibility that the spool might stop its movement in the intermediate location.

SUMMERY OF THE INVENTION

[0008] The present invention has been made in the light of the above problems, and an object thereof is to provide a restarting device of a pump for restarting an operation of the pump automatically in such an event that the operation of the pump is shut down due to a change-over valve stopping in an intermediate position, which valve is to be moved forth and back to switch a direction for a center rod of the pump to move.

[0009] According to a first aspect of the present invention, there is provided a restarting device of a pump in which said pump comprises a center rod defining fluid delivering chambers and driving chambers, wherein when said center rod is driven toward one side, a driving fluid is supplied into one driving chamber located in one side of said center rod so as to discharge a fluid-in-transfer in one fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the other fluid delivering chamber located in the other side of the center rod while the driving fluid in the other driving chamber located in said other side being discharged, and when the center rod is driven toward the other side, the driving fluid is supplied into said other driving chamber located in the other side of the center rod so as to discharge the fluid-in-transfer in said other fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into said one fluid delivering chamber located in said one side of the center rod while the driving fluid in said one driving chamber located in said one side being discharged, so that the fluid-in-transfer may be continuously transferred by the reciprocating motion of said center rod, said restarting device of the pump characterized in comprising: a change-over valve for switching a direction for said center rod to move; and a restarting hydraulic circuit which when a supply of the driving fluid from said change-over valve to the driving chambers in both sides is stopped, detects the supply of the driving fluid into the driving chambers in both sides having been stopped and then causes the driving fluid to flow into said change-over valve, thereby restarting the supply of the driving fluid into said driving chambers.

[0010] According to a second aspect of the present invention, there is provided a restarting device of a diaphragm-type pump in which said diaphragm-type pump comprises a center rod provided with diaphragms in opposite sides thereof, each of said diaphragms defining a fluid delivering chamber and a driving chamber, wherein when said center rod is driven toward one side, a driving fluid is supplied into one driving chamber located in one side of said center rod so as to discharge a fluid-in-transfer in one fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the other fluid delivering chamber located in the other side of the center rod while the driving fluid in the other driving chamber located in said other side being discharged, and when the center rod is driven toward the other side, the driving fluid is supplied into said other driving chamber located in the other side of the center rod so as to discharge the fluid-in-transfer in said other fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into said one fluid delivering chamber located in said one side of the center rod while the driving fluid in said one driving chamber located in said one side being discharged, so that the fluid-in-transfer may be continuously transferred by the reciprocating motion of said center rod, said restarting device of the diaphragm-type pump characterized in comprising: a change-over valve for switching a direction for said center rod to move; and a restarting hydraulic circuit which when a supply of the driving fluid from said change-over valve to the driving chambers in both sides is stopped, detects the supply of the driving fluid into the driving chambers in both sides having been stopped and then causes the driving fluid to flow into said change-over valve, thereby restarting the supply of the driving fluid into said driving chambers.

[0011] According to a third aspect of the present invention, there is provided a restarting device of a diaphragm-type pump in which said change-over valve has a spool, and a pair of pressure chambers is arranged in both sides along the direction for said spool to move, to which a driving fluid is supplied to switch the direction for said spool to move, wherein when said center rod reaches a terminal end of a moving stroke, a pressure difference is generated between the pressures in said pair of pressure chambers so as to switch the position of said spool.

[0012] According to a fourth aspect of the present invention, there is provided a restarting device of a pump in which said pair of pressure chambers are in communication with said both driving chambers via pilot valves respectively, wherein when a direction for said center rod to move is to be switched, a position of the spool is switched in such a way that when the center rod reaches to the terminal end of its moving stroke, the driving fluid in the pressure chamber to be in communication with the driving chamber having the decreased volume is discharged into said driving chamber to drop the pressure in said pressure chamber.

[0013] According to a fifth aspect of the present invention, there is provided a restarting device of a pump in which said restarting hydraulic circuit comprises a three-way check valve unit for detecting a stopped supply of the driving fluid into said respective driving chambers, a check valve unit, and a normally-closed valve unit for releasing the driving fluid from one of said pair of pressure chambers into the atmosphere, said three-way check valve unit having two suction ports and a discharge port, said check valve unit having a suction port and a discharge port, and said normally-closed valve unit having an input port, a suction port and an output port, wherein each of said suction ports of said three-way check valve unit is in communication with each of said driving chambers, said discharge port of said three-way check valve unit is in communication with said suction port of said check valve unit, said discharge port of said check valve unit is in communication with said input port of said normally-closed valve unit, said suction port of said normally-closed valve unit is in communication with one of said pair of pressure chambers, and said output port is open to the atmosphere, said restarting device characterized in that, during said spool being in a reciprocating motion, said suction port and said output port of said normally-closed valve unit are isolated from each other by a pilot pressure, which is generated by supplying the driving fluid from said three-way check valve unit to said check valve unit so as to be applied to said input port, and that, when said spool operationally stops in its intermediate position of the movement, said suction port and said output port are brought into communication with each other due to a decrease of the pilot pressure caused by releasing the driving fluid into an atmosphere via said three-way check valve unit and said check valve unit, and thereby the driving fluid is supplied to one of said pair of pressure chambers through said suction port and said output port, so that a pressure difference is generated between pressures in said pair of pressure chambers, allowing said spool to move from said intermediate position where said spool has stopped toward one side thereof.

[0014] According to a sixth aspect of the present invention, there is provided a restarting device of a diaphragm-type pump in which said restarting hydraulic circuit is incorporated in an interior of a main body of said diaphragm-type pump.

[0015] According to a seventh aspect of the present invention, there is provided a restarting device of a diaphragm-type pump in which said pair of pressure chambers is in communication with said both driving chambers respectively, and when a direction for said center rod to move is to be switched, a position of said spool is switched in such a way that when the center rod reaches to the terminal end of its moving stroke, the driving fluid is supplied into the pressure chamber to be in communication with one of the driving chambers which is different from the driving chamber having the decreased volume, to drop the pressure in said pressure chamber.

[0016] According to an eighth aspect of the present invention, there is provided a restarting device of a pump in which said driving fluid is a compressed air.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a schematic circuit diagram of main components of a restarting device of a pump according to the present invention;

[0018]FIG. 2 is a cross sectional view illustrating an internal configuration of the pump of diaphragm-type shown in FIG. 1;

[0019]FIG. 3 is an enlarged cross sectional view of an internal configuration of the normally-closed valve unit shown in FIG. 1, illustrating a condition where a communication between a suction port and a discharge port is blocked;

[0020]FIG. 4 is an enlarged cross sectional view of an internal configuration of the normally-closed valve unit shown in FIG. 1, illustrating a condition where the suction port and the discharge port are in communication with each other;

[0021]FIG. 5 is an enlarged view of a change-over valve, illustrating a condition where a spool shown in FIG. 1 is positioned in the right hand side;

[0022]FIG. 6 is an enlarged view of a check valve unit shown in FIG. 1, wherein a suction port being in communication with the right chamber thereof;

[0023]FIG. 7 is an enlarged view of the check valve unit shown in FIG. 1, wherein the suction port being in communication with the left chamber thereof; and

[0024]FIG. 8 is an enlarged view of the change-over valve, illustrating the spool shown in FIG. 1 stopping in an intermediate position.

DETAILED DESCRIPTION OF THE INVENTION

[0025]FIG. 1 is a schematic diagram of a hydraulic circuit of a restarting device of a diaphragm-type pump according to the present invention, in which reference numeral 1 is a main body of the diaphragm-type pump, 2 is a change-over valve and 3 is a restarting hydraulic circuit.

[0026] The main body 1 includes, as shown in FIG. 2, a center rod 4 arranged in the center thereof so as to move forth and back in the horizontal direction. A diaphragm 5 is arranged in one end of the center rod 4, and a diaphragm 6 is arranged in the other end of the center rod 4.

[0027] Those diaphragms 5 and 6 are secured at center portions thereof to end portions of the center rod 4 by center discs 7 and 8, and at peripheral portions thereof to mounting portions 9 and 10 of the main body 1 respectively.

[0028] There are spaces 11 and 12 in the both sides of the center rod 4 along the direction of movement so as to permit the center rod 4 to move, said space 11 being segmented into a fluid delivering chamber 11 a and a driving chamber 11 b by the diaphragm 5, and said space 12 being segmented into a fluid delivering chamber 12 a and a driving chamber 12 b by the diaphragm 6.

[0029] A supply path 13 is arranged in a lower portion of the main body 1 for supplying liquid-in-transfer to those fluid delivering chambers 11 a and 12 a, and a discharging path 14 is arranged in an upper portion of the main body 1 for discharging the liquid-in-transfer in the delivering chambers 11 a and 12 a toward the outside. Reference numeral 15 designates an inlet port for receiving the liquid-in-transfer into the supply path 13 from an external unit, and 16 designates a discharge port for discharging the liquid-in-transfer from the discharge path 14 to the outside.

[0030] Suction ports 17 and 18 in communication with the supply path 13 are arranged in lower portions of the fluid delivering chambers 11 a and 12 a, respectively, while discharge ports 19 and 20 in communication with the discharge path 14 are arranged in upper portions of the fluid delivering chambers 11 a and 12 a. The respective ports 17 to 20 are provided with ball valves 21 to 24 serving as check valves for opening and closing those ports 17 to 20.

[0031] The main body 1 is provided with pilot valves 25 and 26 facing to the driving chambers 11 b and 12 b respectively. Those driving chambers 11 b and 12 b are to be supplied with compressed air as driving fluid from the change-over valve 2, which will be described in detail later.

[0032] The change-over valve 2 has a function for switching the direction for the center rod 4 to move. A spool valve has been employed for that change-over valve 2 in this embodiment. The change-over valve 2 has a casing section 25 and a spool 26, as shown in FIG. 1. The casing section 25 includes an accommodation space 27 for allowing the reciprocating motion of the spool 26 along the horizontal direction.

[0033] The spool 26 has a diameter-expanded section 28 in a central portion thereof, and the accommodation space 27 is divided by the diameter-expanded section 28 into the left chamber 27 a and the right chamber 27 b. Other diameter-expanded sections 29 and 30 are formed in the opposite sides of the spool 26 with a portion between the diameter-expanded sections 28 and 29 defined as a diameter-reduced section 31 and another portion between the diameter-expanded sections 28 and 30 as a diameter reduced section 32. Each of the diameter-expanded sections 28 to 30 is provided with a seal member 33.

[0034] The left chamber 27 a has a pressure chamber 27 c, and a back face of the diameter-expanded section 29 is facing to the pressure chamber 27 c. The right chamber 27 a has a pressure chamber 27 d, and a back face of the diameter-expanded section 30 is facing to the pressure chamber 27 d. A small amount of compressed air is supplied to those pressure chambers 27 c and 27 d through small holes respectively, though not shown.

[0035] A snap spring mounting member 34 is arranged in one end portion of the casing section 25, and a snap spring 35 is mounted between one end portion of the spool 26 and the snap spring mounting member 34.

[0036] Air supply ports 36 and 37 are arranged in an upper portion of the casing section 25 for supplying compressed air as a diaphragm driving fluid. The left chamber 27 a is provided with a port 38 and the right chamber 27 b is provided with a port 39. The air supply port 36 is in communication with the port 38, and the air supply port 37 is in communication with the port 39. The port 38 is formed in such a location that the port 38 may be closed by the diameter-expanded section 29 when the spool 26 is positioned in the right hand side, and the port 39 is formed in such a location that the port 39 may be closed by the diameter-expanded section 30 when the spool 26 is positioned in the left hand side.

[0037] The left chamber 27 a is provided with a port 40, the right chamber 27 b is provided with a port 41, and an exhaust port 42 is formed in the casing section 25 at an intermediate location between the left chamber 27 a and the right chamber 27 b. The diameter-expanded section 28 is allowed to move forth and back across the exhaust port 42. The port 40 is brought into communication with the exhaust port 42 when the spool 26 is positioned in the right hand side and the port 41 is brought into communication with the exhaust port 42 when the spool 26 is positioned in the left hand side.

[0038] The pressure chamber 27 c is provided with a port 43 and the pressure chamber 27 d is provided with a port 44. A port 45 is arranged in the casing section 25 between the ports 41 and 44 so as to form a part of a restarting hydraulic circuit 3.

[0039] The port 40 is in communication with the driving chamber 11 b via a connecting pipe 46, the port 41 with the driving chamber 12 b via a connecting pipe 47, and the exhaust port 42 with the atmosphere via an exhaust pipe 48.

[0040] As shown in FIG. 2, the pilot valves 25 and 26 have surge-tanks 25 a and 26 a respectively, and the port 43 shown in FIG. 1 is in communication with the surge-tank 25 a of the pilot valve 25 via a connecting pipe 51 and so as the port 44 with the surge-tank 26 a of the pilot valve 26 via a connecting pipe 52. The surge-tanks 25 a and 26 a serve to charge the compressed air supplied into the pressure chambers 27 c and 27 d. The pilot valves 25 and 26 have normally-closed-valve elements 25 d and 26 d. Tip portions of the normally-closed-valve elements 25 d and 26 d are facing to the center discs 7 and 8 respectively, so as to allow for coming into contact with them.

[0041] The restarting hydraulic circuit 3, when it detects that the supply of the driving fluid from the change-over valve 2 into the both driving chambers 11 b and 12 b has been stopped, works to cause the driving fluid to circulate into the change-over valve 2 thus to restart the supply of the driving fluid into the driving chambers.

[0042] The restarting hydraulic circuit 3 includes a normally-closed valve unit (NC valve), a three-way check valve unit 54, and a check valve unit 55. The normally-closed valve unit 53, as shown in the enlarged views of FIGS. 3 and 4, comprises a movable valve element 57 and a bias spring 58 arranged within a casing portion 56. The casing portion 56 has an input port 59 to which pilot pressure is input, a suction port 60 for suctioning compressed air, and an output port 61 from which the compressed air is output. The movable valve element 57 has a diameter-expanded section 57 a. The diameter-expanded section 57 a serves so as to block a communication between the suction port 60 and the output port 61, and the bias spring 58 serves so as to bias the movable valve element 57 in the direction against the pilot pressure.

[0043] The bias spring 58 is compressed as shown in FIG. 3 while the pilot pressure being input, and the movable valve element 57 is positioned in a location where the suction port 60 is not allowed to communicate with the output port 61, but when there is no more input of the pilot pressure, the movable valve element 57 will be moved by the biasing force from the bias spring 58, as shown in FIG. 4, to a location where the suction port 60 and the output port 61 are in communication with each other.

[0044] The three-way valve unit 54 has two suction ports 68 and 69 and a discharge port 70, and the check valve unit 55 has a suction port 71 and a discharge port 66, said discharge port 66 being in communication with the input port 59 of the normally-closed valve unit 55. The inlet port 59 of the normally-closed valve unit 55 is in communication with either one of the pair of pressure chambers 27 c and 27 d.

[0045] The three-way check valve unit 54 serves to detect that a supply of the driving fluid to the driving chamber 12 b has been stopped, and the check valve unit 55 serves to detect that the supply of the driving fluid to the driving chamber 11 b has been stopped. The check valve unit 55 includes within the casing portion 63 a ball valve 65 functioning as a check valve and a needle valve 67 functioning as a throttle valve. The ball valve 65 serves to open or close the suction port 71. The casing portion 63 thereof is provided with a discharge port 66. The needle valve 67 serves to discharge the compressed air in the discharge port 66 side of the check valve unit 55 into the atmosphere little by little.

[0046] The suction port 68 is in communication with the connecting pipe 47 via a branch pipe 72, so as the suction port 69 with the connecting pipe 46 via a branch pipe 73. The discharge port 70 is connected to the input port 59 of the normally-closed valve unit 53 via a connecting pipe 74.

[0047] The suction port 60 of the normally-closed valve unit 53 is connected to the exhaust port 42 via a compressed air supply pipe 76, and the output port 61 thereof is connected to the connecting pipe 52 via a branch pipe 77.

[0048]FIG. 1 shows a condition where the spool 26 is positioned in the right hand side, the port 40 and the exhaust port 42 are in communication with each other, and the port 39 is open, and accordingly the compressed air is supplied into the driving chamber 12 b via the ports 39 and 41 and the connecting pipe 47 as shown in the enlarged view of FIG. 5 along the path as indicated by the arrow A, and thereby the diaphragm 6 is expanded to drive the center rod 4 to move in the direction as indicated by the arrow B in FIG. 2.

[0049] As the diaphragm 6 is expanded to reduce the volume of the fluid delivering chamber 12 a, the fluid-in-transfer in the fluid delivering chamber 12 a is flown in the direction indicated by the arrow C to be discharged to the outside through the discharge port 16.

[0050] Further, as the center rod 4 is moved in the direction indicated by the arrow B to reduce the volume of the driving chamber 11 b, the compressed air in the driving chamber 11 b is discharged into the atmosphere as indicated by the arrow D′ via the connecting pipe 46, the port 40, the exhaust port 42 and the exhaust pipe 48. At the same time, as the extended volume of the fluid delivering chamber 11 a generates a negative pressure within the fluid delivering chamber 11 a, the fluid-in-transfer is drown along the path indicated by the arrow D via the inlet port 15 and the suction port 17, and thereby the fluid delivering chamber 11 a is filled up with the fluid-in-transfer.

[0051] During a series of those operations, since the compressed air is made flow into the suction port 68 as indicated by the arrow A′ via the port 41 and the branch pipe 72, the compressed air in the three-way check valve unit 54 is supplied to the input port 59 of the normally-closed valve unit 53 via the discharge port 70 and the connecting pipe 74, and the movable valve element 57 of the normally-closed valve unit 53 is held in the condition to block the communication between the suction port 60 and the output port 61.

[0052] On the other hand, during the series of those operations, since the compressed air in the driving chamber 11 b is discharged into the atmosphere via the port 40, the exhaust port 42 and the exhaust pipe 48, the pressure of the compressed air within the branch pipe 73 drops, and consequently the suction port 69 of the check valve unit 55 is closed by the ball valve 65 as shown in the enlarged view of FIG. 7, which prevents the compressed air for pilot to be input to the input port 59 of the normally-closed valve unit 53 via the port 41, the branch pipe 72, the check valve unit 54 and the connecting pipe 74 from flowing into the branch pipe 73 via the check valve unit 55.

[0053] As the center rod 4 is further driven in the direction as indicated by the arrow B to bring the center disc 7 into contact with the normally-closed valve element 25 b of the pilot valve 25 and the center rod 4 reaches to the terminal end of the moving stroke, the compressed air within the surge-tank 25 a is discharged into the driving chamber 11 b to generate a pressure difference between the pressure within the pressure chamber 27 c and the pressure within the pressure chamber 27 d, and thereby the spool 26 is affected by the biasing force of the snap spring 35 to move immediately in the direction indicated by the arrow E, thus allowing the driving direction of the center rod 4 to be switched.

[0054] That is, the position of the spool is switched in such a way that when the center rod reaches to the terminal end of its moving stroke, the driving fluid in the pressure chamber to be in communication with the driving chamber having the decreased volume is discharged into said driving chamber to drop the pressure in said pressure chamber.

[0055] Thereby the port 39 of the right chamber 27 b is closed, and also the port 41 and the exhaust port 42 are brought into communication with each other. On the other hand, the port 38 of the left chamber 27 a is open, and also the communication between the port 40 and the exhaust port 42 is blocked. Accordingly, the compressed air is fed into the driving chamber 11 b through the port 40 and the connecting pipe 46, and the diaphragm 5 is expanded so as to increase the volume of the driving chamber 11 b, while the volume of the fluid delivering chamber 11 a is reduced so as for the fluid-in-transfer within the fluid delivering chamber 11 a to be discharged outside through the discharge port 19 and the discharge path 14.

[0056] On the other hand, as the center rod 4 is moved in the direction reversely to the direction of the arrow B, the volume of the driving chamber 12 b is reduced to increase the volume of the fluid delivering chamber 12 a, and thereby the fluid-in-transfer is drawn into the fluid delivering chamber 12 a through the inlet port 15 and the suction port 18, so that the fluid delivering chamber 12 a is filled up with the fluid-in-transfer.

[0057] During a series of those operations, since the compressed air is fed to the suction port 69 via the port 40 and the branch pipe 73, the suction port 69 of the check valve unit 55 is open, and the compressed air therein is supplied to the input port 59 of the normally-closed valve unit 53 via the discharge port 71 and the connecting pipe 75, so that the movable valve element 57 of the normally-closed valve unit 53 is held in a condition where the communication between the suction port 60 and the output port 61 is blocked. On the other hand, during the series of those operations, since the compressed air in the driving chamber 12 b is discharged into the atmosphere via the port 41, the exhaust port 42 and the exhaust pipe 48, the pressure of the compressed air within the branch pipe 72 decreases, and consequently the suction port 68 of the check valve unit 54 is closed by the ball valve 64, which prevents the compressed air for pilot to be input to the input port 59 of the normally-closed valve unit 53 via the port 40, the branch pipe 73, the check valve unit 55 and the connecting pipe 75 from flowing into the branch pipe 72 via the check valve unit 54.

[0058] In a normal operation mode where the spool 26 of the change-over valve 2 would not stop in the intermediate position, since the pilot pressure is regularly applied to the input port 59 of the normally-closed valve unit 53, the communication between the suction port 60 and the output port 61 thereof is regularly blocked by the movable valve element 57, and the diaphragm-type pump repeats the normal operation as it has been.

[0059] Herein, assuming that the spool stops for some reason in the intermediate position, where the port 38 is blocked by the diameter-expanded section 29, the port 39 is block by the diameter-expanded section 30, and the exhaust port 42 is blocked by the diameter-expanded section 28, the compressed air would not be supplied to the driving chamber 11 b or 12 b through either of the connecting pipe 46 or 47, resulting in the diaphragm-type pump stopping its operation.

[0060] Since those connecting pipes 47 and 46 are brought into communication with the suction ports 68 and 69 of the three-way check valve unit 54 via the branch pipes 72 and 73 respectively, and the needle valve 67 discharges the compressed air in the discharge port 66 side toward the atmosphere little by little, therefore the pilot pressure applied to the input port 59 of the normally-closed valve unit 53 decreases, and the movable valve element 57 is driven from the position as shown in FIG. 3 toward the position as shown in FIG. 4 by the biasing force of the bias spring 58, thereby bringing the suction port 60 in communication with the output port 61 to allow the compressed air having been stored in the compressed air supply pipe 76 to be introduced into the pressure chamber 27 d through the suction port 60, the output port 61, the branch pipe 77 and the connecting pipe 52. This generates a pressure difference between the pressure in the pressure chamber 27 c and that in the pressure chamber 27 d to move the spool 26 along the direction indicated by the arrow F, and the port 38 is brought into communication with the port 40, while the port 41 is brought into communication with the exhaust port 42.

[0061] Thereby, the condition is turned to be such that the compressed air is again supplied to the driving chamber 11 b via the connecting pipe 46, while the compressed air is exhausted from the driving chamber 12 b via the connecting pipe 47, allowing the diaphragm-type pump to restart automatically.

[0062] It is to be noted that the needle valves 66 and 67 functions to prevent a possible occurrence of the chattering phenomenon between the change-over valve 2 and the normally-closed valve unit 53.

[0063] In the foregoing embodiment of the present invention, the pressure difference is generated between the pressure in the pressure chamber 27 c and that in the pressure chamber 27 d by decreasing the pressure of either one of the pressure chambers 27 c or 27 d to cause the spool to move, the present invention is also applicable to such a configuration in which either one of the pressure chambers 27 c or 27 d may have its pressure increased to cause the spool 26 to move.

[0064] In the foregoing embodiment, the present invention is applied to a diaphragm-type pump. However, the present invention can also be applied to an air-drive type piston pump or a bellows pump.

[0065] Moreover, in the foregoing embodiment of the present invention the restarting hydraulic circuit 3 is arranged externally to the main body 1 of the diaphragm-type pump. However, the restarting hydraulic circuit 3 can also be arranged within the main body 1.

EFFECT OF THE INVENTION

[0066] According to the present invention, even if the operation of a pump stops due to a change-over valve stopping in an intermediate location, which has been moved forth and back to switch the movable direction of a center rod of the pump, the operation of the pump can be restarted automatically. 

What is claimed is:
 1. A restarting device of a pump in which said pump comprises a center rod defining fluid delivering chambers and driving chambers, wherein when said center rod is driven toward one side, a driving fluid is supplied into one driving chamber located in one side of said center rod so as to discharge a fluid-in-transfer in one fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the other fluid delivering chamber located in the other side of the center rod while the driving fluid in the other driving chamber located in said other side being discharged, and when the center rod is driven toward the other side, the driving fluid is supplied into said other driving chamber located in the other side of the center rod so as to discharge the fluid-in-transfer in said other fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into said one fluid delivering chamber located in said one side of the center rod while the driving fluid in said one driving chamber located in said one side being discharged, so that the fluid-in-transfer may be continuously transferred by the reciprocating motion of said center rod, said restarting device of the pump characterized in comprising: a change-over valve for switching a direction for said center rod to move; and a restarting hydraulic circuit which when a supply of the driving fluid from said change-over valve to the driving chambers in both sides is stopped, detects the supply of the driving fluid into the driving chambers in both sides having been stopped and then causes the driving fluid to flow into said change-over valve, thereby restarting the supply of the driving fluid into said driving chambers.
 2. A restarting device of a diaphragm-type pump in which said diaphragm-type pump comprises a center rod provided with diaphragms in opposite sides thereof, each of said diaphragms defining a fluid delivering chamber and a driving chamber, wherein when said center rod is driven toward one side, a driving fluid is supplied into one driving chamber located in one side of said center rod so as to discharge a fluid-in-transfer in one fluid delivering chamber located in said one side, and the fluid-in-transfer is suctioned into the other fluid delivering chamber located in the other side of the center rod while the driving fluid in the other driving chamber located in said other side being discharged, and when the center rod is driven toward the other side, the driving fluid is supplied into said other driving chamber located in the other side of the center rod so as to discharge the fluid-in-transfer in said other fluid delivering chamber located in said other side, and the fluid-in-transfer is suctioned into said one fluid delivering chamber located in said one side of the center rod while the driving fluid in said one driving chamber located in said one side being discharged, so that the fluid-in-transfer may be continuously transferred by the reciprocating motion of said center rod, said restarting device of the diaphragm-type pump characterized in comprising: a change-over valve for switching a direction for said center rod to move; and a restarting hydraulic circuit which when a supply of the driving fluid from said change-over valve to the driving chambers in both sides is stopped, detects the supply of the driving fluid into the driving chambers in both sides having been stopped and then causes the driving fluid to flow into said change-over valve, thereby restarting the supply of the driving fluid into said driving chambers.
 3. A restarting device of a diaphragm-type pump in accordance with claim 2, in which said change-over valve has a spool, and a pair of pressure chambers is arranged in both sides along the direction for said spool to move, to which a driving fluid is supplied to switch the direction for said spool to move, wherein when said center rod reaches a terminal end of a moving stroke, a pressure difference is generated between the pressures in said pair of pressure chambers so as to switch the position of said spool.
 4. A restarting device of a diaphragm-type pump in accordance with claim 3, in which said pair of pressure chambers are in communication with said both driving chambers via pilot valves respectively, wherein when a direction for said center rod to move is to be switched, a position of said spool is switched in such a way that when said center rod reaches to the terminal end of its moving stroke, the driving fluid in the pressure chamber to be in communication with the driving chamber having a decreased volume is discharged into said driving chamber to drop the pressure in said pressure chamber.
 5. A restarting device of a diaphragm-type pump in accordance with claim 4, in which said restarting hydraulic circuit comprises a three-way check valve unit for detecting a stopped supply of the driving fluid into said respective driving chambers, a check valve unit, and a normally-closed valve unit for releasing the driving fluid from one of said pair of pressure chambers into the atmosphere, said three-way check valve unit having two suction ports and a discharge port, said check valve unit having a suction port and a discharge port, and said normally-closed valve unit having an input port, a suction port and an output port, wherein each of said suction ports of said three-way check valve unit is in communication with each of said driving chambers, said discharge port of said three-way check valve unit is in communication with said suction port of said check valve unit, said discharge port of said check valve unit is in communication with said input port of said normally-closed valve unit, said suction port of said normally-closed valve unit is in communication with one of said pair of pressure chambers, and said output port is open to the atmosphere, said restarting device characterized in that, during said spool being in a reciprocating motion, said suction port and said output port of said normally-closed valve unit are isolated from each other by a pilot pressure, which is generated by supplying the driving fluid from said three-way check valve unit to said check valve unit so as to be applied to said input port, and that, when said spool operationally stops in its intermediate position of the movement, said suction port and said output port are brought into communication with each other due to a decrease of the pilot pressure caused by discharging the driving fluid into an atmosphere chamber via said three-way check valve unit and said check valve unit, and thereby the driving fluid in one of said pair of pressure chambers is released into the atmosphere through said suction port and said output port, so that a pressure difference is generated between pressures in said pair of pressure chambers, allowing said spool to move from said intermediate position where said spool has stopped toward one side thereof.
 6. A restarting device of a diaphragm-type pump in accordance with claim 5, in which said restarting hydraulic circuit is incorporated in an interior of a main body of said diaphragm-type pump.
 7. A restarting device of a diaphragm-type pump in accordance with claim 3, in which said pair of pressure chambers is in communication with said both driving chambers respectively, and when a direction for said center rod to move is to be switched, a position of said spool is switched in such a way that when said center rod reaches to the terminal end of its moving stroke, the driving fluid is supplied into the pressure chamber to be in communication with one of the driving chambers which is different from the driving chamber having the decreased volume, to drop the pressure in said pressure chamber.
 8. A restarting device of a pump in accordance with any one of the claim 1 to 7, in which said driving fluid is a compressed air. 